1. Field of the Invention
This invention generally relates to a pneumatic spring comprising an elastic expansion bellows, a receptacle fastened to the expansion bellows, at least one fastening element between the expansion bellows and the receptacle, a point where an assembly comprising the pneumatic spring is attached to the vehicle chassis, a shock absorber having a piston rod and an outer tube, the outer tube representing an unrolling surface for the expansion bellows, and connection mechanisms on the piston rod and on the shock absorber outer tube respectively for the attachment of the pneumatic spring shock absorber unit inside a vehicle chassis.
2. Background Information
German Laid Open Patent Application No. 21 03 152 discloses a pneumatic spring in connection with a shock absorber, on which an expansion bellows, or rolling bellows is connected to the shock absorber by means of a tape tensioning element. As an axial safety device and/or to reduce the radial space required for the installation of the tape tensioning element, the outer tube of the shock absorber has a circular bead, such as an annular indentation, in which the tape tensioning element and the expansion bellows are fastened. One of several disadvantages of this solution is that the outer tube of the shock absorber must be fabricated individually for each application. The number of motor vehicles equipped with pneumatic springs is relatively small, however, which means that consideration must be given to the fact that each type of vehicle frequently requires its own individual shock absorbers. Therefore the solution proposed by German Laid Open Patent Appln. No. 21 03 152 does not appear to be economical in terms of the fabrication costs required for the production of small series.
German Patent No. 31 16 466 discloses a process for the installation of an expansion bellows with a shock absorber. Apparently, a standard shock absorber can advantageously be used without modifications of the shock absorber outer tube, but the installation process is quite complicated. A particular disadvantage relating to the safety of the finished product is that the welded joint between the receptacle and the piston rod must essentially provide support for the receptacle and simultaneously perform a sealing function for the pneumatic spring. There are also major problems relating to painting, since the shock absorbers are coated with corrosion protection agents only after they have been installed on the vehicle.
This embodiment and the assembly process also essentially rule out any retrofitting of an existing shock absorber with a pneumatic spring in a repair shop. Nor should the major effort required to remove the shock absorber be underestimated, since the separation of the pneumatic spring from the shock absorber can be very complex and time-consuming.